Linear balanced free piston machines

ABSTRACT

The invention provides a novel class of linear balanced free piston machines which include a first movable assembly supported for reciprocating movement along an inner axis, at least two counterbalancing assemblies supported for individual reciprocating movement along respective separate paths spaced around the inner axis, and a corresponding plurality of separate synchronizing mechanisms individually connecting each counterbalancing assembly to the first movable assembly for simultaneous synchronized movement of the counterbalancing assemblies along their respective paths with component vectors of such movement directed at all times in the opposite direction to the movement of the first assembly. At least one of the movable assemblies includes a movable member of an energy absorbing device, such as a compressor, electric generator or pump. The parts are arranged and interrelated to maintain the common center of gravity of all moving masses of the apparatus at a substantially fixed location therein for all operating positions of the respective assemblies. Preferred arrangements of individual synchronizing levers and of a cooperating sealing member between such inner and outer movable assemblies are shown.

United States Patent [191 Braun [451 Jan. 14, 1975 LINEAR BALANCED FREE PISTON MACHINES [76] lnventor: Anton Braun, 6421 Warren Ave.,

Minneapolis, Minn. 55435 [22] Filed: Feb. 16, 1973 [21] Appl. N0.: 333,069

[52] US. Cl. 123/46 R, 60/DIG. 1, 123/46 B, 123/192 B, 123/192 R, 417/313, 417/343 [51] Int. Cl. F02b 71/00, F02d 39/10 [58] Field of Search. 60/D1G. 1; 123/192 B, 192 R, 123/46 R, 46 B; 417/343, 313

[56] References Cited UNITED STATES PATENTS 662,631 11/1900 Steele 123/192 R 2,244,215 6/1941 Pescara.. 74/110 1 2,442,470 6/1948 Pescara 123/46 2,876,751 3/1959 Kolthoff 123/46 2,991,773 7/1961 Cadiou 123/46 SC 3,501,087 3/1970 Benaroya [23/46.

3,525,102 8/1970 Braun 123/46 R, 3,610,214 10/1971 Braun 123/46 R 3,610,216 10/1971 Braun... 123/192 B 3,610,217 10/1971 Braun 123/192 Primary Examiner-Manuel A. Antonakas Assistant Examiner-Daniel J. OConnor Attorney, Agent, or Firm-Dorsey, Marquart, Windhorst, West & Halladay [57] ABSTRACT The invention provides a novel class of linear balanced free piston machines which include a first movable assembly supported for reciprocating movement along an inner axis, at least two counterbalancing assemblies supported for individual reciprocating movement along respective separate paths spaced around the inner axis, and a corresponding plurality of separate synchronizing mechanisms individually connecting each counterbalancing assembly to the first movable assembly for simultaneous synchronized movement of the counterbalancing assemblies along their respective paths with component vectors of such movement directed at all times in the opposite direction to the movement of the first assembly. At least one of the movable assemblies includes a movable member of an energy absorbing device, such as a compressor, electric generator or pump.

The parts are arranged and interrelated to maintain thecommon center of gravity of all moving masses of the apparatus at a substantially fixed location therein for all operating positions of the respective assemblies.

Preferred arrangements of individual synchronizing levers and of a cooperating sealing member between such inner and outer movable assemblies are shown.

14 Claims, 10 Drawing Figures PATENTEU JAN I 4|975 SHEET 1 BF 3 l LINEAR BALANCED FREE PISTON MACHINES BACKGROUND OF THE INVENTION Free piston engines are known in which power is transmitted from a suitable power piston to a movable member of an energy absorbing device by connections within the engine. In some of these machines, the desired balance is achieved by connecting a power piston and energy absorbing device member, such as a compressor piston, to move together as a unit, and by providing a substantially identical unit movable along the same axis as the first unit and at all times in opposite directions. In such machines, a member of a particular function, such as a power piston, moving with one unit is counterbalanced by a substantially identical member such as another similar power piston moving in the opposite direction with the other unit. Thus the balancing is achieved by an arrangement of two oppositely moving assemblies which are essentially symmetrical, i.e. which constitute substantially mirror images of each other on each side of a central axis or plane of symmetry.

As described and claimed in my earlier US. Pat. Nos. 3,501,088 and 3,525,102, unsymmetrical free piston engines have been developed in which two oppositely moving counterbalancing assemblies which are not symmetrical, for one reason or another, are arranged to balance each other.

There are problems, however, when one wishes to utilize such prior free piston engine devices for applications in which it is necessary or desirable to isolate part or all of one of the movable assemblies from the other.

Forexample, if the energy absorbing device in such an apparatus is to operate on food materials for human or animal consumption, there is a need to insure that the food product handled by the machine cannot be contaminated by oil or other impurities from the power section of such an engine. Similarly in such applications as refrigeration, it may be important to seal off or isolate an energy absorbing device, such as a compressor or pump for the refrigerant, from the power section of the machine or from the atmosphere or other surroundings. In any case, it is desirable to prevent the escape of oil or other contaminants from the power section of a free piston engine.

The desired isolation of such movable working or energy absorbing members from their associated driving engine power sections or surroundings has been previously achieved in other types of machines, such as rotary machines by the use of appropriate rotary seals. In piston machines where reciprocating translational movement of power and working pistons along the same axis is involved, it is possible to achieve some isolation by special seals or packings along an axially movable piston shaft extending between the power and working pistons. Such arrangements, however, involve greater axial length for the entire machine and extra expense for the cost of the packings. The extent and speed of axial movement of the parts also tends to wear out the seals prematurely.

SUMMARY OF THE INVENTION The present invention provides a novel class of free piston machines in which a first movable assembly is mounted for reciprocating movement with its center of gravity moving along an inner axis, and in which at least two counterbalancing assemblies are mounted for individual reciprocating, i.e., back and forth, movement with the respective centers of gravity of the counterbalancing asemblies moving along separate individual paths spaced from each other around such axis. A separate synchronizing mechanism connects each respective counterbalancing assembly with the first movable assembly for movement of the counterbalancing assembly along its path with a component vector of movement which is at all times opposite to the direction of movement of the first assembly along the inner axis. The machine further includes at least one power cylinder stationarily mounted in the engine, and one of the movable assemblies includes a power piston portion movable within the power cylinder, while at least one of the other movable assemblies includes a movable member of an energy absorbing device. Such device may be partly or entirely driven by transmission of forces from such a power cylinder to the energy absorbing device member through the particular synchronizing mechanism which connects the two assemblies. To further achieve the desired balance, the respective paths of movement of the counterbalancing assemblies are angularly oriented and spaced around the inner axis, and the construction and operation of the respective synchronizing mechanisms are so arranged, that the common center of gravity of all moving masses within the machine remains at a substantially fixed point therein for all operating positions of the respective assemblies. The outer assemblies are preferably spaced symmetrically around the inner axis to simplify the design considerations.

Free piston machines according to the invention may include a plurality of power piston portions carried by one or more of the movable assemblies, but preferably by less than all of the assemblies. Such plural power piston portions may be connected and operated to provide simultaneous or parallel power strokes for the assembly or assemblies involved, or to provide successively alternating power strokes in first one direction and then the opposite direction.

In one operating form of the invention, two or more counterbalancing assemblies are movable along paths which are parallel to the inner axis of the machine, are separated therefrom by equal radial distances and are spaced around said axis at equal angular spacings, with the masses of the respective counterbalancing assemblies equal to each other and with the center of gravity of the first movable assembly moving at all times along said inner axis. In the preferred form of the invention, the first movable assembly includes two alternately and oppositely acting power piston portions movable coaxially along the inner axis, all power pistons of the machine are included in the first movable assembly, and two counterbalancing assemblies are located with their parallel paths of movement spaced apart around the inner axis and with two alternately and oppositely acting compressor piston portions on one of these two counterbalancing movable assemblies and with the other counterbalancing movable assembly operating essentially only as a counterbalancing mass.

In order to achieve the desired synchronizing action while maintaining the center of gravity of all moving parts at the desired common point, the preferred synchronizing mechanism for each counterbalancing assembly includes a lever having an intermediate part pivotally supported on the machine for limited swinging movement on a pivotal axis perpendicular to the common plane defined by the respective inner path or axis of movement of the first movable assembly and the path of movement of the particular outer counterbalancing assembly. This pivotal axis is thus spaced between the two assemblies, and the lever has ends projecting toward each assembly and connected thereto by respective inner and outer links. For maximum elimination or balancing of components of vibration, the synchronizing lever and its links should have a Z-shaped configuration as shown in the accompanying drawings, with the inner and outer connecting links projecting in opposite parallel directions from the outer ends of the synchronizing lever to the respective movable assemblies. Moreover, the length of the synchronizing lever should be selected with reference to the desired distances through which the inner and outer assemblies are to reciprocate, so that the synchronizing lever swings through equal arcs, as small as practically possible, above and below a reference line passing through the pivotal axis of the lever and perpendicular to the paths of movement of the assemblies.

To provide the desired separation of the power sections from the energy absorbing or working members, all power piston portions are preferably located on one movable assembly, i.e., the inner or first movable assembly, and this assembly is enclosed within a first housing portion. The working members can then be positioned on one or more of the counterbalancing assemblies, each within its own outer or second housing portion. These housing portions are sealed from each other by suitable housing or partition walls, except for a limited area at which a transverse passageway is provided to accommodate a synchronizing mechanism lever. Thus, according to a further feature of the invention, a flexible sealing partition can be positioned across the limited passageway between the first movable assembly and the counterbalancing assemblies, such sealing member being penetrated only by the rocking lever of its synchronizing mechanism and being sealed around such rocking lever close to the pivotal axis of the synchronizing lever. In this construction, sealing surface displacements and velocities can be much lower than on conventional shaft or similar sealing. surfaces running at the same speeds and distances as the movable assemblies themselves, and the usual rubbing velocities which wear out such conventional seals are eliminated and replaced by limited flexing of a sealing partition.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which form a part of this application, and in which like reference characters indicate like parts FIG. 1 is a schematic elevation view, partly in section, of one operating form of linear balanced free piston machine according to the invention, in which a reciprocating inner power assembly is individually connected to and counterbalanced by two outer oppositely movable counterbalancing assemblies, each of which includes a movable member of an energy absorbing device.

FIG. 2 is a schematic top view of a modified form of such a machine in which a central assembly is connected to three outer counterbalancing assemblies;

FIG. 3 is a view similar to FIG. 2 of a free piston machine of this type in which a central assembly is connected to four oppositely moving outer counterbalancing assemblies spaced at equal angles around the axis of the inner assembly;

FIG. 4 is a view similar to FIGS. 2 and 3 ofa modified free piston machine in which an inner movable assembly is connected to four oppositely moving outer counterbalancing assemblies which are not distributed at equal angles from each otheraround the inner assembly, but which are symmetrically spaced around the axis of the inner assembly in balanced pairs;

FIG. 5 is a view similar to FIG. 2 of a modified free piston machine in which an inner movable assembly includes at least one pair of pistons at opposite sides of the axis of movement of the inner assembly, and in which this assembly is counterbalanced by two oppositely moving outer counterbalancing assemblies;

FIG. 6 is a view similar to FIG. 1 of a modified linear balanced free piston machine in which the inner assembly is a power assembly which is individually connected to two movable outer assemblies, one of which includes a movable member of an energy absorbing device, while the other assembly serves primarily as part of the counterbalancing weight for the inner assembly;

FIG. 7 is a'view similar to FIGS. 1 and 6 of a further modification inwhich power pistons are mounted on each of two outer counterbalancing assemblies, while the inner movable assembly performs only a balancing function;

FIG. 8 is a view similar to FIG. 6 of a preferred free piston machine in which an inner movable assembly has two coaxial alternately and oppositely acting power pistons and is individually connected to two oppositely moving outer counterbalancing assemblies, and one of which includes a pair of alternately and oppositely acting compressor piston portions and the other of which operates only as a part of the counterbalancing mass;

FIG. 9 is an enlarged sectional view on the line 9 9 of FIG. 8 (but with the synchronizing lever in its midposition), showing details of a flexible sealing member and synchronizing lever combination according to the invention; and

FIG. 10 is a sectional view on the line 10 10 of FIG. 9, with portions broken away for clearness.

' DESCRIPTION OF THE PREFERRED EMBODIMENTS tional movement along an inner longitudinal axis of the machine. In this embodiment, the first movable assembly includes a power piston portion 13 which reciprocates within a power cylinder 14 stationarily mounted on the housing or frame 11. A fuel injector or spark plug 16, and appropriate inlet and outlet ports, provide for compression ignition or spark ignition of an appropriate combustible mixture within the combustion chamber 17 between the piston portion 13 and the head of cylinder 14 in known manner.

Piston 13 is secured to a longitudinally movable shaft 18, which in this case is co-axial with piston 13 and cylinder l4 and defines an inner axis or path of longitudinal movement of the first movable assembly.

At the lower end of shaft 18 is secured a connecting member 19 for the synchronizing mechanisms to be described below, together with a further piston portion 21 designed to reciprocate along the axis 18 within a lower cylinder 22. The space between piston portion 21 and the head of the cylinder portion 22 may serve as any desired portion of a free piston engine power section, and may, as in FIG. 8, constitute another combustion chamber to provide power during successive power strokes in opposite directions for inner assembly 12. Alternatively, chamber 23 may serve as a bounce compressor chamber to provide return energy for upward movement of the inner assembly 12, or it may serve as a scavenging chamber to provide air for scavenging the combustion chamber 17. Chamber 23 may also serve as a part of an energy absorbing device such as a compression chamber in which the piston 21 serves as the movable member of such a device to provide desired pressures or pumping actions within chamber 23.

As described, the first movable assembly 12 includes a plurality of portions or members, all of which move essentially as a unit during the reciprocating translational movement of this assembly.

According to the present invention, at least two counterbalancing assemblies are supported for reciprocating translational movement along paths which are spaced outwardly from and around the inner axis of the first movable assembly l2. In this embodiment, two such counterbalancing assemblies are shown, as indicated generally at 24 and 26 respectively. Counterbalancing assembly 24 includes a movable member 27 of an energy absorbing device, which is illustrated as a compressor piston working in a compressor cylinder 28 provided with appropriate inlet and outlet ports 29 and 31. In this embodiment the second counterbalancing assembly 26 also comprises a movable energy absorbing device member and is shown as a compressor piston 32 operating in compressor cylinder 33 with an inlet 34 and outlet 36. Other forms of energy absorbing devices, such as generators, pumps, or the like could also be advantageously incorporated or substituted for these particular counterbalancing members. Compressors 28 and 33 may be independent, or connected in parallel as parts of a single stage compressor, or connected in series for two stage compression.

According to a further feature of the invention, each outer counterbalancing assembly is individually connected by a separate synchronizing device to the first movable inner assembly 12. The respective counterbalancing assemblies are symmetrically positioned around the axis 18 in a manner which is determined by the relative masses of the moving parts incorporated in or moving with the various movable assemblies, and the paths of movement of the counterbalancing assemblies and their relative angular spacings around the inner axis 18 are selected in such a manner that the common center of gravity of all moving masses of the machine remains at a substantially fixed location in the engine for all operating positions of the respective assemblies. In this particular case, the paths of movement of the outer counterbalancing assemblies are parallel to the inner axis 18, the masses of the respective counterbalancing asemblies are equal to each other, and their paths of movement are spaced at equal radial distances from the inner axis 18 and at equal angular distances around that axis, i.e., 180 apart from each other as measured around the axis 18.

The individual synchronizing mechanisms are constructed and oriented to provide movement of each counterbalancing assembly in directions having component vectors of such movement which move at all times in the opposite direction to the direction of movement of the inner assembly 12.

A preferred synchronizing mechanism is shown in FIG. 1, in which a swinging or oscillating lever 37 is pivoted on a transverse axis at 38 fixed in housing 11 and extending in a direction perpendicular to the common plane defined by the axis of movement of shaft 18 and the axis of movement of piston 27. The pivotal axis 38 of lever 37 is thus located, as shown, at an intermediate position between the paths of movement of the respective assemblies which are connected by the lever.

Lever 37 has its outer lever end arm 39 pivotally con nected at 41 to a connecting link 42, which is pivoted in turn at 43 to the compressor piston 27. The opposite or inner end 44 of the lever 37 is pivoted at 46 to another connecting link 47, the lower end of which is pivoted at 48 to the member 19 of the first movable assembly 12. The axes of rotation of all of these pivots are parallel to each other in this embodiment.

A similar synchronizing lever 49 is pivoted at 51 to connect the other counterbalancing assembly 26 to the first assembly 12. Lever 49 has its outer end pivoted to a connecting link 53, which is pivoted to compressor piston 32, while the inner end of the lever 49 is similarly pivoted to a connecting link 52 pivoted to member 19 of the first movable assembly 12.

To achieve the desired balance, and to minimize or eliminate lateral or rotary unbalanced forces, the two synchronizing mechanisms are constructed in similar fashion and are symmetrically oriented, so that rotation or swinging movement of one element of one synchronizing mechanism is symmetrically balanced by an opposite rotation or swinging movement of a corresponding element of the other synchronizing mechanism. It will be understood that if more than two counterbalancing assemblies and individual synchronizing devices are used according to the invention, they would be arranged symmetrically with respect to axis 18 in such a way that the desired condition of balance would be achieved. Also, as illustrated in FIG. 1, the respective arms of levers 37 and 49 are equal, i.e., the counterbalancing assemblies move along their paths over the same total distances as the inner or first movable assembly 12. The lever arms could in some cases be unequal for special design needs, e.g., to achieve the proper compatibility between the power piston speed and the speed of a pump piston or other working member. The desired balance is achieved in each case by making sure that the absolute values of the product of the masses moving in one direction times the lengths of their respective strokes are equal at all times to the absolute values of the masses moving in the opposite direction times the lengths of their strokes.

Also, the paths of movement of the counterbalancing assemblies need not be parallel to the path of movement of the first movable assembly 12, provided that the angular orientation of the various paths of movement of the two or more outer counterbalancing assemblies according to the invention are so arranged, and the relative masses moving along the different paths, the lengths of their moving strokes, and the construction and orientation of the individual synchronizing connections between such outer assemblies and the inner or first movable assembly all cooperate and are interrelated to maintain the common center of gravity of all moving masses of the machine at a fixed location in the engine for all operating positions of the engine assemblies. In the example of FIG. 1,-the center of gravity of the moving parts of the first assembly 12 are symmetrically located with respect to the shaft axis 18, so that the common center of gravity of all members of the first movable assembly 12 remains at all times somewhere along the shaft axis 18. The various masses of the counterbalancing assemblies and synchronizing mechanism parts are similarly arranged in this case to have their common center of gravity likewise located along the shaft axis 18 in such a manner that they substantially completely counterbalance the first movable assembly, a condition which is defined when the common center of mass of all the movable masses which form a part of or move with the various assemblies and synchronizing connections of the machine remains at a substantially fixed location within the machine, i.e., in this case at a particular fixed point along the shaft axis 18.

FIGS. 2 to 4 are schematic top views of modified forms of linear balanced free piston machines'according to the invention in which the relative number or arrangement of counterbalancing assemblies may be varied within the principles already set foith. Thus FIG. 2 is a schematic top view of a modification in which a first movable assembly, indicated generally at 71, is movable along an axis 72 in a direction which would be perpendicular to the plane of the drawing as viewed in FIG. 2. In this case, three counterbalancing assemblies 73, 74 and 76 are spaced around the axis 72 at equal angular distances from each other and at equal radial distances from the axis 72 itself. Each .of the counterbalancing assemblies 73, 74 and 76 is individually movable on its own axis parallel to the axis 72 of the first movable assembly. Each of these counterbalancing assemblies is also individually and separately connected to the first movable assembly by appropriate synchronizing linkages essentially similar to those shown in the device of FIG. 1-. The main levers 77, 78 and 79 of the respective individual synchronizers are shown in FIG. 2 as oscillating on fixed pivots 81, 82 and 83 suitably fixed within a main housing or frame 84 of the machine. These main levers are connected by appropriate intermediate links (not shown) to the respective pivotal connections 86, 87 and 88 of the respective counterbalancing assemblies, as well as to the parallel pivotal axes 89, 91 and 92 on the first movable assembly. In this case, as well as in the modifications of FIGS. 3, 4 and 5, the synchronizing levers are pivoted at their midpoints so that the relative lengths of reciprocating movement of the first movable assembly and of each counterbalancing assembly are essentially the same.

In the particular configuration shown in the modification of FIG. 2, the total mass of each counterbalancing assembly 73, 74 and 76 is equal to one-third of the total mass of the first movable assembly 71. It would be possible to provide synchronizing levers which have arms of unequal length, and to space the counterblancing assemblies angularly at other relatively symmetrical positions around the first movable assembly, for example with two of the three counterbalancing assemblies relatively close to each other and with the third counterbalancing assembly located at the opposite side of thefirst movable assembly at an angular location half way between the first two counterbalancing assemblies, in which case the masses of the respective counterbalancing assemblies would be adjusted with respect to each other to achieve the balancing condition previously described, i.e., in which the common center of gravity of all moving masses of the apparatus remains at a substantially fixed position within the machine at all operating positions of the various assemblies.

FIG. 3 illustrates another modification in which a first movable inner assembly 93 is individually connected to four outer movable counterbalancing assemblies 94, 96, 97 and 98, by means of individual synchronizing levers 99, 101, 102 and 103 respectively. Here again, the various assemblies are individually movable with respect to a main housing or frame 104, and the individual paths of movement of the outer counterbalancing assemblies, as well as their lengths of stroke and relative masses are so chosen as to position the common center of gravity of all movable masses of the machine at a fixed location in the machine for all operating positions. In this case, the outer counterbalancing assemblies are spaced at equal angles around the axis of the inner assembly 93, i.e., apart, the main synchronizing levers have arms of equal lengths, so that the relative lengths of travel of the respective assemblies are equal,'and to achieve the desired balancing condition, each of the counterbalancing assemblies has a total mass equal to one quarter of the mass of the inner movable assembly, with each counterbalancing mass at the same radial distance outwardly from the axis of movement of the inner movable assembly 93.

FIG. 4 shows a modified arranngement in which an inner movable assembly'106 reciprocates on an axis 107 relative to a machine frame or housing 108, and in which the movement of the first assembly is balanced by four outer counterbalancing assemblies 109, 111, 112 and 113. These outer counterbalancing assemblies are individually connected by separate synchronizing levers 114, 116, 117 and 118 respectively to the inner movable assembly 106 in such a manner that the outer assemblies have the desired component vectors of movement at all times in the opposite direction to the movement of the inner assembly 106. In this case, the four outer counterbalancing assemblies are symmetrically spaced with respect to axis 107, but are not spaced at equal angles from each other around that axis. Instead, the four outer counterbalancing assemblies are located in symmetrical pairs, so that assemblies 109 and 111 are angularly close to each other and are symmetrically balanced by diametrically opposite assemblies 112 and 113 which are also relatively close to each other on the opposite side of axis 107. Here again the respective arms of the synchronizing levers 114, etc. are equal, so that the respective inner and outer assemblies travel along parallel paths for equal distances in opposite directions to achieve the desired condition of balance.

FIG. 5 shows another modification of the invention in which the inner assembly indicated generally at 119 is movable along an inner axis 121 and includes two piston members 123 and 124 which are rigidly connected as parts of the first movable assembly 119 and are symmetrically positioned so that the center of mass of the first assembly remains at some point along axis 121, while all parts of the first assembly move together as a unit with respect to the machine housing or frame 122.

In this case two counterbalancing assemblies 127 and 128 are located apart around axis 121 and are supported for individual movement along paths parallel to axis 121. Each counterbalancing assembly is individually connected by a separate synchronizing member, such as synchronizing levers 129 and 131 respectively, to the inner movable assembly 119, so that each of the outer assemblies always moves in the opposite direction to the direction of movement of the inner assembly. Here again the synchronizing levers are supported for limited oscillation on fixed rotary axes 132 and 133 respectively.

In each of the arrangements shown in FIGS. 2 to 5, there will be at least one power piston on one of the movable assemblies and at least one movable member of an energy absorbing device on another of the movable assemblies. For example, each of the inner movable assemblies of FIGS. 2 to could involve a power piston for driving each respective machine, while at least one, or even all of the outer counterbalancing assemblies could include a movable compressor piston or other movable energy absorbing device member. Alternately, such an energy absorbing device member can be included in at least one, but less than all of the outer counterbalancing assemblies, and the remaining counterbalancing assembly or assemblies may constitute merely a counterbalancing weight, or may perform some other function which does not necessarily classify it as an energy absorbing device.

FIG. 6 shows another modification of this latter type. In this modification the first movable assembly 136 includes a power piston 138 reciprocating in a stationary power cylinder 139 fixed with respect to the housing or frame portion 137. A connecting shaft 141 rigidly connects the power piston 138 to a second piston 142 which moves as a unit with the other parts of assembly 136 and operates within a second cylinder 143 to provide any desired operating function. In this case cylinder 143 preferably serves to provide a bounce chamber or scavenging chamber for cooperation with the power cylinder 139.

All of the parts of this first assembly. move together as a unit along the longitudinal axis 144 of the machine which preferably constitutes an axis of symmetry of this first assembly, so that the center of mass of all movable elements of the first assembly is located at all times somewhere along axis 144,

In the device of FIG. 6 two outer counterbalancing assemblies are provided. The first counterbalancing assembly 146 includes an energy absorbing device member which is illustrated as a compressor piston 147 operating within a compressor cylinder 148. In this example, the compressor piston 147 is connected by a shaft 149 to a longitudinally movable cross-head 151 which slides within guide 152 to insure the desired path of movement of this outer counterbalancing assembly. The assembly 146 is individually connected to the first inner movable assembly 136 by a synchronizing lever 153 pivoted at 154 for limited swinging movement on a fixed axis on housing 137 at a point intermediately spaced between the inner and outer movable assemblies. Lever 153 in this case has two equal arms, one of which is pivoted at 156 to a connecting link 157, the other end of which is pivoted at 158 to crosshead 151. Similarly, the inner end of lever 153 is pivoted at 159 to a symmetrical connecting link 161, the other end of which is pivoted at 162 to a portion 163 secured to the inner movable assembly 136 and moving as a unit therewith. Thus the synchronizing linkage just described insures movement of counterbalancing assembly 146 at all times with a major component vector of such movement (and in this case with the entire direction of such movement) extending always in the opposite direction to the movement of the first assembly 5 The second counterbalancing assembly 164 in the modification of FIG. 6 is illustrated as one which performs only a counterbalancing function and which includes no movable energy absorbing device member. In this case the assembly has a shaft portion 166 fixed to a crosshead 167 vertically movable in guide 168 on portion 169 of the main housing 137. At the upper end of shaft 166 a further crosshead member 171 moves within guide member 172, with all parts of the counterbalancing assembly 164 moving as a unit along a path parallel to axis 144 and spaced from that axis a radial distance equal to the spacing of counterbalancing assembly 146. Here the elements 166, 167 and 171 of the counterbalancing assembly move as a unit, and are individually connected by the separate synchronizing lever 173 and the intermediate links 174 and 176 to the portion 163 of the inner assembly to obtain the desired balancing movement of assembly 164 at all times in the opposite direction to the movement of the inner assembly 136.

In this and other cases, the outer arm portions of the synchronizing levers, such as 153 and 173, can not only differ in length from the inner portions, but may even differ in length from each other, provided the relative outer lever arm lengths and the masses of theouter assemblies connected to them are selected to maintain the desired condition of balance, with the common center of gravity ofall movable masses of the complete FIG. 7 schematically illustrates another modification in which the inner movable assembly 181 constitutes essentially a counterweight which is movable similarly to a crosshead within guide 182 of the main frame or housing of the apparatus. The outer counterbalancing assemblies 183 and 184 in this configuration each include piston members. For example assembly 183 includes a power piston 186 and the compressor piston 187, while assembly 184 similarly includes a power piston 188 and a compressor piston 189. In each of these outer assemblies, there is essentially a complete free piston engine portion, all parts of which move together as a unit in one direction. The individually movable outer assemblies are connected by separate synchronizing levers 191 and 192, and the intermediate linkage connections previously described, to the inner movable assembly 181, which then moves in the opposite direction as a counterbalancing weight to provide the specified condition of balance for the entire machine. Alternately, the inner movable assembly 181 could include a pump piston, compressor piston or other working member.

Another modification of the invention is shown in FIGS. 8, 9 and 10. In FIG. 8, the inner movable assembly 221 includes upper and lower power pistons 222 and 223 which move along a common axis within coaxial upper and lower power cylinders 224 and 226. A connecting shaft 227 rigidly interconnects the power pistons for movement of this inner assembly as a unit.

An outer housing portion 228 is provided at one side of the main housing of the inner power unit, and this outer housing encloses one of the outer movable assemblies 229, which consists of upper and lower compres'sor pistons fwithina compressor cylinder 233 and the compressor includes inletandoutlet valves 234 and 236. The lower compressor piston 232 operates within its own lower compressor cylinder portion-237, which also has appro- 231 jand 232. Piston 231 reciprocates priate inlet and outlet valves 238 and 239. A rigid connecting shaft -240;conne cts,1 the upper and lower power 'piston sfor movement of all parts of thisouter assembly as a-unit.- The'main housing; portion 24'1 has a projectin'g flange aiea 242 which is adapted toengage one'surface of an intermediat'eimember 243, which is secured betweenpo'iftion 2421 anda cooperating flange portion Y 244 on the'ou'terhousingi 228,10 provideappropriate lines of separation between thelinner and outer housing's and =mem'berj243. Thus the-respecting housing portions 24'! and 228 effectiyely separate the'inner and outer jmovableassemblies from each other; but provide a transverse passageway'246 extending transversely between the two housi'ngs'zThe synchronizing mechanism for-separately interconnecting the outer assemblyj229 with the, inner assembly- 221 includes a transversely extending. lever 247. which projects through passageway 1 246 and which'is. providedwitha pivotal ,support'in at least one of: the housing niernbers 242gi 243" and 244; In

this case, as shown in detail in, F1659, lever'247 includes an inne'rend' 248 with a bearing 249ifor pivotal connection'with a link"2f5l; The other end of link 251 bodiment of FlG. 8, however; has the distinct advantage that the free piston machine is provided with positivepower strokesin both directionsofope'ration and these power strokes-occur in-this particular example along the common axis of. movem'ent of the two power pistons on the-innermovable-assembly This device therefore does not depend on the return energy 'of a bounce -compressor,.for its return strokes, and there-is no need to adjust any such bounce return energy during starting, for .exar npl je during. the transition from an ini-- tialfstarting stroketonorrnal operation; Moreover,

work v is performed by; one .energyabsorbing devicem'ember in one direction of move.-

.me'n't' and by another such membifliin: the opposite dir'ectio'n of movement -Instead of two separate oppositelyact'ing workingmemb'ers, a single member which vis double-actingcan-be provided, such asacompr'e's'sor I piston with twov oppositely acting faces. I Also, where maximum speed of operation'is' desired; theFlGi 8 ariscOnn'ected at252'to a cross member 253 rigidly's'e- 'L'ever247'ha a'm'ain' mass-mos 254 extending a j 'vbt 'li gea in 2565a: i s one end for ai'p vota n-l nection tof alin'k 257; the'other end of-whieh is pivoted- .at 258 to't'hefout'ermovable'assernbly229iv v lnjthis casejthe pivotal support for leveri247 is pro- 'videdb'y two' angulariy projecting arin's261 and262 whichterminate in shaft portions 263 and 2641pivotally supported in bearings 266 and; 267. These bearing poriv tions are secured between the respective inner and intermediate members 242 and 243' so marine pivotal axis isgenerally along the plane of separation 245 betweenthese two members.

members 269 and27l movablejverticallywithin guides j; The remainingremovable outer assembly shown. in FICL'S is thecounterbalancing assembly 268i'iilhich is illl'istrated as having upper and lower counterweight 272 and'273 along an outer path essentially parallel to the path of inner shaft 227. A connecting shaft 274 rigidly interconnects counter-weights 269 and 271 for movement of the parts of this counterbalancing assembly as a unit.

The desired:counterbalancing movement is provided by ;a separate synchronizing lever 275, pivoted at 276 in one of the housing portions for pivotal movement on an axis essentially perpendicular .to the common plane defined by shafts 227 and 274. Thus, similarly'to lever 247; the outer end'of lever' 275 is secured through a connecting link 277 to the outer movable assembly 268, while the innerendof lever 275 is similarlysecured by a connecting link 278 to the rigid portion 253 of the inner movable assembly. Thus all movements of the inner assembly-221 are counterbalanced at all times by opposite" movements of the respective outer assembliesr229 and 268. In this case only'one of the outer assemblies involves any working or energy-absorbing dea vice, whilethe other'outer counterbalancing assembly performs merely apart of the counterbalancing function without any corresponding work function. The emb t q ut lu o a BIG stroke and'bore';

power output foffthe'enginelAlsog as seen by comparison with'FlQ. 6:, only-asniall'iricrease'in size'a'nd cost is necessary .to' providejthe increased power. output 'of such aFlG. s e' of machine. which is morehthanfdou lnall these caseggm masses are so balanced that eommoncenteriof gra I I I I I I entire unit remains at: asubstantially v fixed location in the machinev for all operating positionsof the respective assemblies. Furthermore, in this-FI GLLS r pe or ma- .ofall movable masses of the chine, all of thepower functions are concentratedin i j the, inner or main housing-portion as partof the inner or first movable assembly. a v

- According to a further feature of the invention, it is desirable in many casesto provideva positive seal or separation between the operating mechanisms of the inner assemblyandone or more'of the outer assemblies;v The'present invention provides an im'proved'arrangementfor such a seal in combination with the particular orientation and relative arrangement of the parts of this type of free piston-machine. Such a sealing arrangement is shown at the left portion of FIG. 8 between the inner assembly 221 and the outer assembly 229, and further details of an appropriate sealingmembet and arrangement are further shown in-FIGS. 9 and 10. Thusa flexible sealing member or diaphragm 281 movement provided by bearing shafts 263 and 264.

is provided which has an inner edge secured in sealing engagement to lever member 247, and specifically to a suitable seat 282 located on the central portion 254 oflever 247 at a point essentially along the axis of pivotal The outer edge of flexible diaphragm member' 281 is secured at 284 to anyappropriate housing portion, and is shown herein between the housing portion 243 and an outer retaining member 286 secured to the housing portion 243 by screws 287.

lt will beunderstood that the specific design of a flex- I ible sealing member such as 281 may be :varied to tit the particular application involved. Also, the manner of securing the inner and outer edges of such a sealing member can be modified by those skilled-in the art. ln

iite with' th same power any case, however, this invention positions the sealing engagement between such a sealing member 281 and the movable rocker arm or lever of the synchronizing mechanism in a plane which either intersects or is close to the pivotal axis of the lever member. Thus both the physical displacement of the sealing member and the degree of flexing imparted to it by movement of the lever can be reduced to a minimum and the life of such a sealing member correspondingly increased. In effect, the sealing member is secured to the lever arm at a point where the sealing surfacedisplacements and velocities are much lower than on any of the conventional shaft or similar surfaces in prior art devices, where such sealing surfaces must be running at the same speed or moving along the same axial distances as the pistons of a prior art engine configuration. The particular lever arrangement shown in FIGS. 9 and 10, with the Y- shaped portions 261 and 262 extending outwardly to hearing shafts 263 and 264 makes it possible in this particular caseto anchor the inner edge of the sealing member 281 at exactly the location of the pivotal axis of the lever, by means of the retaining clamp 283 and associated bolts. Thus a novel and advantageous sealing arrangement is provided in the particular combination of the present invention in which an inner movable assembly and an outer movable assembly move in essentially parallel paths and in opposite directions, and in which the motion is transmitted between these assemblies in the desired manner by means of a rocking lever extending generally transversely from the inner assembly to the outer assembly and pivoted for rocking movement on a pivotal axis which is essentially perpendicular to the common plane defined by the paths of movement of the inner and outer assemblies. In this way, a sealing member associated with such a rocking lever close to its pivotal axis is subjected to minimum flexing and displacement, in terms of both distance and velocity and allows hermetic sealing.

As shown in the devices of FIGS. 7 and 8, a plurality of power pistons are located on one or more, but less than all, of the inner and outer movable assemblies. In the example of FIG. 7, one power piston portion is carried by each of the outer movable assemblies, and the inner movable assembly has no power piston. The two power pistons are arranged to provide simultaneous power strokes in only one direction of movement of the respective assemblies.

In the FIG. 8 embodiment, the free piston machine is provided with plural power piston portions which are arranged for alternating and successive power strokes and resulting driving movement of the assemblies successively in opposite directions. Thus work may be performed by one or more energy absorbing device members in one direction of movement and by one or more other such members in the opposite direction of movement. This type of arrangement provides a machine in which the working and power functions may be substantially equally balanced. The machine also has its masses balanced so that the common center of gravity of all movable masses of the entire unit remains at a substantially fixed location in the machine for all operating positions of the respective assemblies.

The balanced linear free piston machines described in the foregoing specification are believed to offer significant advantages in both flexibility of design and construction, and in minimizing production costs for a line of such machines in which standardized individual elements such as power pistons, power cylinders, synchronizing linkages, compressor cylinders and pistons and the like can be assembled in various configurations to meet the requirements of different applications.

Such machines have a design flexibility which can be adapted to a wide range of different applications and functions, including not only pumps, generators and compressors broadly, but also including operation with different products or fluids, such as air, refrigeration gases or other gases. The preferred combination of a specific synchronizing lever arrangement and flexible sealing member as arranged in this novel class of free piston machines also provides for hermetic sealing between the respective movable assemblies and their housings to meet the requirements for relative isolation of any materials or any parts ofthe machine, either with respect to each other or the surrounding environment. The specifications set forth some of the ways in which the invention may be practiced, including the best mode presently contemplated for carrying out the invention. Other modifications and variations may be apparent to those skilled in the art, in the light of the foregoing description and the following claims.

I claim:

1. A balanced linear free piston machine comprising a first movable assembly having portions substantially all of which move together asa unit, said first movable assembly being supported for reciprocating movement with its center of gravity moving along an inner longitudinal axis of the machine, at least two movable counterbalancing assemblies each of which has portions substantially all of which move together as a unit, each counterbalancing assembly being supported for individual separate reciprocating movement with the respective centers of gravity of the counterbalancing assemblies moving along respective separate outer paths spaced from each other around said inner axis and first movable assembly, a separate synchronizing means mechanically and independently interconnecting each movable counterbalancing assembly with said first movable assembly for simultaneous synchronized movement of each movable counterbalancing assembly along its path in a direction having component vectors of such movement which are moving at all times in the opposite direction to the movement of the first movable assembly, at least one power cylinder stationarily mounted on said machine, one of the movable assemblies having a power piston portion supported for reciprocating movement in said power cylinder, and at least one of the other movable assemblies including a movable member of an energy absorbing device.

2. A balanced linear free piston machine according to claim 1 in which the paths of movement of the movable counterbalancing assemblies are angularly oriented and spaced around the inner axis at positions determined by the relative masses and lengths of stroke of the respective movable counterbalancing assemblies and of the first movable assembly, the relative location and orientation of said plurality of paths and the construction, orientation and operation of said synchronizing devices positioning all of the masses included in and associated and moving with each movable counterbalancing assembly at radial distances and angularly spaced positions around said inner axis and first movable assembly which maintain the common center of gravity of all moving masses of the apparatus in a substantially fixed position in the apparatus at all possible operating positions of the movable assemblies.

3. A balanced linear free piston machine according to claim 1 in which at least one, but less than all, of said movable assemblies is provided with a power piston.

4. A balanced linear free piston machine according to claim 1 in which at least two of said movable assemblies are each provided with at least one power piston and in which the power pistons of different movable assemblies are movable in respectively different paths.

5. A balanced linear free piston machine according to claim 1 in which said one power cylinder is coaxial with said inner axis and said one power piston portion is also coaxial therewith, said power piston portion being part of said first movable assembly for movement of said first assembly in response to power strokes of the power piston portion coaxially along said inner axis in at least one direction, and with the center of mass of the first assembly located at all times on said inner axis.

6. A balanced linear free piston machine according to claim 5 in which the first movable assembly includes two oppositely acting power piston portions for movement of the first assembly in response to successive alternating power strokes of the two power piston portions along said inner axis in both directions.

7. A balanced linear free piston machine according to claim 6 in which the counterbalancing movable assemblies include at least one first working member which performs work during movement of the first movable assembly in one direction and at least one second working member which performs work during movement of the first movable assembly in the opposite direction.

8. A balanced. linear free piston machine according to claim 5 having two counterbalancing assemblies supported for movement along respective separate paths each of which is parallel to said inner axis and spaced 180 around said inner axis and first movable assembly from the other separate path.-

9. A balanced linear free piston machine according to claim 8 in which the two counterbalancing assemblies are of substantially equal mass and their respective paths of movement are spaced radially equal distances from said inner axis and first movable assembly.

10. A balanced linear free piston machine according to claim 9 in which only one of the two counterbalancing assemblies includes a movable energy absorbing device member and the other counterbalancing assembly operates only as a counterbalancing mass.

11. A balanced linear free piston machine according to claim 10 in which only the first movable assembly is provided with any power piston.

12. A balanced linear free piston machine according to claim 1 in which a second power cylinder is stationarily mounted on said machine, and one of the other movable assemblies has a power piston portion supported forreciprocating translational movement in said second power cylinder.

13. A balanced linear free piston machine according to claim 1 having a first housing portion for the first movable assembly and a second housing portion for one of the other movable assemblies, said first and second housing portions having wall portions generally separating said movable assemblies from each other but providing a limited transverse connecting passageway between them, the synchronizing device connecting the first movable assembly to said one other movable assembly including a lever extending through said passageway generally transversely from said inner axis toward the outer path of movement of said one other movable assembly, said lever having a pivotal support on one of the housing portionsclose to said passageway for pivotal movement of the lever on a pivotal axis generally perpendicular to a plane defined by said inner axis and by said outer path of movement, and a flexible sealing member extending across and sealing said passageway and having sealing engagement with said lever close to its pivotal axis.

14. A balanced linear free piston engine according to claim 13 in which said flexible sealing member has its outer edges clamped in sealing engagement against at least one of said first and second housing portions. 

1. A balanced linear free piston machine comprising a first movable assembly having portions substantially all of which move together as a unit, said first movable assembly being supported for reciprocating movement with its center of gravity moving along an inner longitudinal axis of the machine, at least two movable counterbalancing assemblies each of which has portions substantially all of which move together as a unit, each counterbalancing assembly being supported for individual separate reciprocating movement with the respective centers of gravity of the counterbalancing assemblies moving along respective separate outer paths spaced from each other around said inner axis and first movable assembly, a separate synchronizing means mechanically and independently interconnecting each movable counterbalancing assembly with said first movable assembly for simultaneous synchronized movement of each movable counterbalancing assembly along its path in a direction having component vectors of such movement which are moving at all times in the opposite direction to the movement of the first movable assembly, at least one power cylinder stationarily mounted on said machine, one of the movable assemblies having a power piston portion supported for reciprocating movement in said power cylinder, and at least one of the other movable assemblies including a movable member of an energy absorbing device.
 2. A balanced linear free piston machine according to claim 1 in which the paths of movement of the movable counterbalancing assemblies are angularly oriented and spaced around the inner axis at positions determined by the relative masses and lengths of stroke of the respective movable counterbalancing assemblies and of the first movable assembly, the relative location and orientation of said plurality of paths and the construction, orientation and operation of said synchronizing devices positioning all of the masses included in and associated and moving with each movable counterbalancing assembly at radial distances and angularly spaced positions around said inner axis and first movable assembly which maintain the common center of gravity of all moving masses of the apparatus in a substantially fixed position in the apparatus at all possible operating positions of the movable assemblies.
 3. A balanced linear free piston machine according to claim 1 in which at least one, but less than all, of said movable assemblies is provided with a power piston.
 4. A balanced linear free piston machine according to claim 1 in which at least two of said movable assemblies are each provided with at least one power piston and in which the power pistons of different movable assemblies are movable in respectively different paths.
 5. A balanced linear free piston machine according to claim 1 in which said one power cylinder is coaxial with said inner axis and said one power piston portion is also coaxial therewith, said power piston portion being part of said first movable assembly for movement of said first assembly in response to power strokes of the power piston portion coaxially along said inner axis in at least one direction, and with the center of mass of the first assembly located at all times on said inner axis.
 6. A balanced linear free piston machine according to claim 5 in which the first movable assembly includes two oppositely acting power piston portions for movement of the first assembly in response to successive alternating power strokes of the two power piston portions along said inner axis in both directions.
 7. A balanced linear free piston machine according to claim 6 in which the counterbalancing movable assemblies include at least one first working member which performs work during movement of the first movable assembly in one direction anD at least one second working member which performs work during movement of the first movable assembly in the opposite direction.
 8. A balanced linear free piston machine according to claim 5 having two counterbalancing assemblies supported for movement along respective separate paths each of which is parallel to said inner axis and spaced 180* around said inner axis and first movable assembly from the other separate path.
 9. A balanced linear free piston machine according to claim 8 in which the two counterbalancing assemblies are of substantially equal mass and their respective paths of movement are spaced radially equal distances from said inner axis and first movable assembly.
 10. A balanced linear free piston machine according to claim 9 in which only one of the two counterbalancing assemblies includes a movable energy absorbing device member and the other counterbalancing assembly operates only as a counterbalancing mass.
 11. A balanced linear free piston machine according to claim 10 in which only the first movable assembly is provided with any power piston.
 12. A balanced linear free piston machine according to claim 1 in which a second power cylinder is stationarily mounted on said machine, and one of the other movable assemblies has a power piston portion supported for reciprocating translational movement in said second power cylinder.
 13. A balanced linear free piston machine according to claim 1 having a first housing portion for the first movable assembly and a second housing portion for one of the other movable assemblies, said first and second housing portions having wall portions generally separating said movable assemblies from each other but providing a limited transverse connecting passageway between them, the synchronizing device connecting the first movable assembly to said one other movable assembly including a lever extending through said passageway generally transversely from said inner axis toward the outer path of movement of said one other movable assembly, said lever having a pivotal support on one of the housing portions close to said passageway for pivotal movement of the lever on a pivotal axis generally perpendicular to a plane defined by said inner axis and by said outer path of movement, and a flexible sealing member extending across and sealing said passageway and having sealing engagement with said lever close to its pivotal axis.
 14. A balanced linear free piston engine according to claim 13 in which said flexible sealing member has its outer edges clamped in sealing engagement against at least one of said first and second housing portions. 